scholarly journals Comparison of Different Approaches to Predict the Performance of Pumps As Turbines (PATs)

Energies ◽  
2018 ◽  
Vol 11 (4) ◽  
pp. 1016 ◽  
Author(s):  
Mauro Venturini ◽  
Stefano Alvisi ◽  
Silvio Simani ◽  
Lucrezia Manservigi
Keyword(s):  
Simulation Model ◽  
Ad Hoc ◽  
Polynomial Regression ◽  
Point Of View ◽  
Box Model ◽  
Physical Point ◽  
Evolutionary Polynomial Regression ◽  
Box Models ◽  
Performance Curves ◽  
Physics Based Simulation

This paper deals with the comparison of different methods which can be used for the prediction of the performance curves of pumps as turbines (PATs). The considered approaches are four, i.e., one physics-based simulation model (“white box” model), two “gray box” models, which integrate theory on turbomachines with specific data correlations, and one “black box” model. More in detail, the modeling approaches are: (1) a physics-based simulation model developed by the same authors, which includes the equations for estimating head, power, and efficiency and uses loss coefficients and specific parameters; (2) a model developed by Derakhshan and Nourbakhsh, which first predicts the best efficiency point of a PAT and then reconstructs their complete characteristic curves by means of two ad hoc equations; (3) the prediction model developed by Singh and Nestmann, which predicts the complete turbine characteristics based on pump shape and size; (4) an Evolutionary Polynomial Regression model, which represents a data-driven hybrid scheme which can be used for identifying the explicit mathematical relationship between PAT and pump curves. All approaches are applied to literature data, relying on both pump and PAT performance curves of head, power, and efficiency over the entire range of operation. The experimental data were provided by Derakhshan and Nourbakhsh for four different turbomachines, working in both pump and PAT mode with specific speed values in the range 1.53–5.82. This paper provides a quantitative assessment of the predictions made by means of the considered approaches and also analyzes consistency from a physical point of view. Advantages and drawbacks of each method are also analyzed and discussed.

Simulation Model of the Dynamic Behavior of a Tire Running Over an Obstacle

1988 ◽  
Vol 16 (2) ◽  
pp. 62-77 ◽  
Author(s):  
P. Bandel ◽  
C. Monguzzi
Keyword(s):  
Simulation Model ◽  
Dynamic Behavior ◽  
Black Box ◽  
Box Model ◽  
Vehicle Suspension ◽  
Empirical Relationships ◽  
Static Tests ◽  
High Speeds ◽  
Dynamic Forces ◽  
Vehicle Suspension System

Abstract A “black box” model is described for simulating the dynamic forces transmitted to the vehicle hub by a tire running over an obstacle at high speeds. The tire is reduced to a damped one-degree-of-freedom oscillating system. The five parameters required can be obtained from a test at a given speed. The model input is composed of a series of empirical relationships between the obstacle dimensions and the displacement of the oscillating system. These relationships can be derived from a small number of static tests or by means of static models of the tire itself. The model can constitute the first part of a broader model for description of the tire and vehicle suspension system, as well as indicating the influence of tire parameters on dynamic behavior at low and medium frequencies (0–150 Hz).

GROUNDWATER TIME SERIES

1970 ◽  
Vol 1 (3) ◽  
pp. 181-205 ◽  
Author(s):  
ERIK ERIKSSON
Keyword(s):  
Time Series ◽  
Point Of View ◽  
Hydrologic Models ◽  
Physical Point ◽  
Run Off ◽  
Fort Collins ◽  
Statistical Sense ◽  
Full Benefit ◽  
Future Work ◽  
Prediction Problems

The term “stochastic hydrology” implies a statistical approach to hydrologic problems as opposed to classic hydrology which can be considered deterministic in its approach. During the International Hydrology Symposium, held 6-8 September 1967 at Fort Collins, a number of hydrology papers were presented consisting to a large extent of studies on long records of hydrological elements such as river run-off, these being treated as time series in the statistical sense. This approach is, no doubt, of importance for future work especially in relation to prediction problems, and there seems to be no fundamental difficulty for introducing the stochastic concepts into various hydrologic models. There is, however, some developmental work required – not to speak of educational in respect to hydrologists – before the full benefit of the technique is obtained. The present paper is to some extent an exercise in the statistical study of hydrological time series – far from complete – and to some extent an effort to interpret certain features of such time series from a physical point of view. The material used is 30 years of groundwater level observations in an esker south of Uppsala, the observations being discussed recently by Hallgren & Sands-borg (1968).

scholarly journals Percolation and tortuosity in heart-like cells

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
R. Rabinovitch ◽  
Y. Biton ◽  
D. Braunstein ◽  
I. Aviram ◽  
R. Thieberger ◽  
...  
Keyword(s):  
Action Potential ◽  
Forest Fire ◽  
Sinus Node ◽  
Heart Tissue ◽  
Point Of View ◽  
Physical Point ◽  
Electrical Currents ◽  
Single Wave ◽  
Heart Arrhythmia ◽  
The One

AbstractIn the last several years, quite a few papers on the joint question of transport, tortuosity and percolation have appeared in the literature, dealing with passage of miscellaneous liquids or electrical currents in different media. However, these methods have not been applied to the passage of action potential in heart fibrosis (HF), which is crucial for problems of heart arrhythmia, especially of atrial tachycardia and fibrillation. In this work we address the HF problem from these aspects. A cellular automaton model is used to analyze percolation and transport of a distributed-fibrosis inflicted heart-like tissue. Although based on a rather simple mathematical model, it leads to several important outcomes: (1) It is shown that, for a single wave front (as the one emanated by the heart's sinus node), the percolation of heart-like matrices is exactly similar to the forest fire case. (2) It is shown that, on the average, the shape of the transport (a question not dealt with in relation to forest fire, and deals with the delay of action potential when passing a fibrotic tissue) behaves like a Gaussian. (3) Moreover, it is shown that close to the percolation threshold the parameters of this Gaussian behave in a critical way. From the physical point of view, these three results are an important contribution to the general percolation investigation. The relevance of our results to cardiological issues, specifically to the question of reentry initiation, are discussed and it is shown that: (A) Without an ectopic source and under a mere sinus node operation, no arrhythmia is generated, and (B) A sufficiently high refractory period could prevent some reentry mechanisms, even in partially fibrotic heart tissue.

scholarly journals A parameter-free total Lagrangian smooth particle hydrodynamics algorithm applied to problems with free surfaces

2021 ◽  
Author(s):  
Kenny W. Q. Low ◽  
Chun Hean Lee ◽  
Antonio J. Gil ◽  
Jibran Haider ◽  
Javier Bonet
Keyword(s):  
Ad Hoc ◽  
Wide Spectrum ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Point Of View ◽  
Numerical Dissipation ◽  
Lagrangian Description ◽  
Smooth Particle Hydrodynamics ◽  
Particle Hydrodynamics ◽  
Sph Algorithm

AbstractThis paper presents a new Smooth Particle Hydrodynamics computational framework for the solution of inviscid free surface flow problems. The formulation is based on the Total Lagrangian description of a system of first-order conservation laws written in terms of the linear momentum and the Jacobian of the deformation. One of the aims of this paper is to explore the use of Total Lagrangian description in the case of large deformations but without topological changes. In this case, the evaluation of spatial integrals is carried out with respect to the initial undeformed configuration, yielding an extremely efficient formulation where the need for continuous particle neighbouring search is completely circumvented. To guarantee stability from the SPH discretisation point of view, consistently derived Riemann-based numerical dissipation is suitably introduced where global numerical entropy production is demonstrated via a novel technique in terms of the time rate of the Hamiltonian of the system. Since the kernel derivatives presented in this work are fixed in the reference configuration, the non-physical clumping mechanism is completely removed. To fulfil conservation of the global angular momentum, a posteriori (least-squares) projection procedure is introduced. Finally, a wide spectrum of dedicated prototype problems is thoroughly examined. Through these tests, the SPH methodology overcomes by construction a number of persistent numerical drawbacks (e.g. hour-glassing, pressure instability, global conservation and/or completeness issues) commonly found in SPH literature, without resorting to the use of any ad-hoc user-defined artificial stabilisation parameters. Crucially, the overall SPH algorithm yields equal second order of convergence for both velocities and pressure.

scholarly journals Promoting Interpersonal Relationships through Elbow Tag, a Traditional Sporting Game. A Multidimensional Approach

2021 ◽  
Vol 13 (14) ◽  
pp. 7887
Author(s):  
Verónica Muñoz-Arroyave ◽  
Miguel Pic ◽  
Rafael Luchoro-Parrilla ◽  
Jorge Serna ◽  
Cristòfol Salas-Santandreu ◽  
...  
Keyword(s):  
Decision Making ◽  
Social Interactions ◽  
Interpersonal Relationships ◽  
Predictive Power ◽  
Ad Hoc ◽  
Scientific Evidence ◽  
Point Of View ◽  
Registration System ◽  
Motor Behaviors ◽  
Quasi Experimental

The aim of this research was to study from a multidimensional point of view (decisional, relational and energetic) the interpersonal relationships established by girls and boys in the traditional sport game of Elbow Tag. Scientific evidence has shown that Traditional Sport Games (TSG) trigger different effects on male and female genders in relation to emotional experiences, decision-making, conflicts and motor relationships. Despite the fact that these dimensions are intertwined, there are hardly any studies that interpret motor behaviors holistically, i.e., taking a multidimensional (360°) view of these dimensions. For this study, a quasi-experimental design was used and a type III design was applied, inspired by the observational methodology N/P/M. A total of 147 university students participated (M = 19.6, SD = 2.3): 47 girls (31.97%) and 100 boys (68.02%). A mixed ‘ad hoc’ registration system was designed with acceptable margins of data quality. Cross-tabulations, classification trees and T-patterns analysis were applied. The results indicated that social interactions between girls and boys in a mixed group were unequal. This difference was mainly due to decision-making (sub-role variable), which has much greater predictive power than the energetic variables (MV and steps).

Fidelity enhancement of a rotorcraft simulation model through system identification

2011 ◽  
Vol 115 (1170) ◽  
pp. 453-470 ◽  
Author(s):  
L. Lu ◽  
G. D. Padfield ◽  
M. White ◽  
P. Perfect
Keyword(s):  
System Identification ◽  
Simulation Model ◽  
Linear Models ◽  
Aircraft Design ◽  
Design Data ◽  
Loads Analysis ◽  
Physics Based Simulation ◽  
Six Degree Of Freedom ◽  
The University ◽  
Frequency Domain Approach

AbstractHigh fidelity modelling and simulation are prerequisites for ensuring confidence in decision making during aircraft design and development, including performance and handling qualities, control law developments, aircraft dynamic loads analysis, and the creation of a realistic simulation environment. The techniques of system identification provide a systematic framework for ‘enhancing’ a physics–based simulation model derived from first principles and aircraft design data. In this paper we adopt a frequency domain approach for model enhancement and fidelity improvement of a baseline FLIGHTLAB Bell 412 helicopter model developed at the University of Liverpool. Predictability tests are based on responses to multi–step control inputs. The techniques have been used to generate one, three, and six degree-of-freedom linear models, and their derivatives and predictability are compared to evaluate and augment the fidelity of the FLIGHTLAB model. The enhancement process thus involves augmenting the simulation model based on the identified parameters. The results are reported within the context of the rotorcraft simulation fidelity project, Lifting Standards, involving collaboration with the Flight Research Laboratory (NRC, Ottawa), supported with flight testing on the ASRA research helicopter.

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